Aneurysms in the abdominal aorta are associated with particularly high mortality rates. Current medical standards call for urgent operative repair. Abdominal surgery results in substantial stress to the body, and particularly in cases of aortic aneurysm, the mortality rate is extremely high. There is also considerable mortality and morbidity associated with open surgical intervention to repair an aortic aneurysm. This intervention involves penetrating the abdominal wall to the location of the aneurysm to reinforce or replace the diseased section of the aortic aneurysm. A prosthetic device, typically a synthetic tube graft, is used for this purpose. The graft serves to exclude the aneurysm from the circulatory system, thus relieving pressure and stress on the weakened section of the aorta at the aneurysm.
Repair of an aortic aneurysm by surgical means is a major operative procedure. Substantial morbidity accompanies the procedure, resulting in a protracted recovery period. Furthermore and as mentioned herein, the procedure entails a substantial risk of mortality. While surgical intervention may be indicated and the surgery carries attendant risk, certain patients may not be able to tolerate the stress of intra-abdominal surgery. It is, therefore, desirable to reduce the mortality and morbidity associated with intra-abdominal surgical intervention.
Anastomosis is the surgical fusion of biological tissues, especially joining tubular organs to create an inter communication between them. Vascular surgery often involves producing an anastomosis between blood vessels or between a blood vessel and a vascular graft to create or restore a blood flow path to essential tissues. The first successful aortic resection for aneurysm was performed in 1951.
One anastomosis method involves harvesting a vein in the body using an artificial conduit made of Dacron or Goretex tubing, and connecting the conduit as a bypass graft from a viable artery, such as the aorta, to the coronary artery downstream of the blockage or narrowing. A graft with both the proximal and the distal ends of the graft detached is known as a “free graft”.
A second method involves rerouting a less essential artery, such as the internal mammary artery, from its native location so that it may be connected to the coronary artery downstream of the blockage. The proximal end of the graft vessel remains attached in its native position.
Until about a decade ago, essentially all vascular anastomosis were performed by conventional hand suturing. Suturing the anastomosis is a time-consuming and difficult task, requiring much skill and practice on the part of the surgeon. It is important that each anastomosis provides a smooth, open flow path for the blood and that the attachment be completely leaks-proof. A completely leak-proof seal is not always achieved on the very first try. Consequently, there is a frequent need for re-suturing the anastomosis to close any leaks that are detected. The time consuming nature of hand-sutured anastomosis is disadvantageous for several reasons. First, circulatory isolation and cardiac arrest are inherently very traumatic, and it has been found that the frequency of certain post-surgical complications varies directly with the duration for which the heart is under cardioplegic arrest (frequently referred to as the “crossclamp time”). Secondly, because of the high cost of cardiac operating room time, any prolongation of the surgical procedure can significantly increase the cost of the bypass operation to the hospital and to the patient. Thus, it is desirable to reduce the duration of the cross clamp time and of the entire surgery by expediting the anastomosis procedure without reducing the quality or effectiveness of the anastomosis.
The already high degree of manual skill required for conventional manually sutured anastomosis is even more demanding for closed-chest or port-access thoracoscopic bypass surgery. A newly developed surgical procedure designed to reduce the morbidity as compared to the standard open-chest procedure described in U.S. Pat. Nos. 5,452,733 and 5,735,290. In the closed-chest procedure, surgical access to the heart is made through narrow access ports made in the intercostal spaces of the patient's chest, and the procedure is performed under thoracoscopic observation. Because the patient's chest is not opened, the suturing of the anastomosis must be performed at some distance, using elongated instruments positioned through the access ports for approximating the tissues and for holding and manipulating the needles and sutures used to make the anastomosis. This requires even greater manual skill than the already difficult procedure of suturing anastomosis during open-chest surgery.
The biggest drawback of such an anastomosis is that it requires a fair amount of mobility of the two vessel ends to allow easy and accurate placement of the sutures, and it has a tendency to be constrictive.
In order to reduce the difficulty of creating the vascular anastomosis, there was a need to provide a rapid means for making a reliable anastomosis between a bypass graft or artery and the aorta or the native vessels of the heart. A first approach to expediting and improving anastomosis procedures has been through stapling technology. Stapling technology has been successfully employed in many different areas of surgery for making tissue attachments faster and more reliably. The greatest progress in stapling technology has been in the area of gastrointestinal surgery. Various surgical stapling instruments have been developed for anastomosis of hollow or tubular organs, such as the bowel. These instruments, unfortunately, are not easily adaptable for use in creating vascular anastomosis. This is partially due to the difficulty in miniaturizing the instruments to make them suitable for smaller organs such as blood vessels. Possibly even more important is the necessity of providing a smooth, open flow path for the blood. Known gastrointestinal stapling instruments for anastomosis of tubular organs are designed to create an inverted anastomosis in which the tissue folds inward into the lumen of the organ that is being attached. This is acceptable in gastrointestinal surgery, where it is most important to approximate the outer layers of the intestinal tract. However, in vascular surgery, this geometry is unacceptable for several reasons. First, the inverted vessel walls would cause a disruption in the blood flow. This could cause decreased flow and ischemia downstream of the disruption, or, yet worse, the flow disruption or eddies could become a locus for thrombosis that could shed emboli or occlude the vessel at the anastomosis site.
Secondly, unlike the intestinal tract, the outer surfaces of the blood vessels will not grow together when approximated. The sutures, staples, or other joining device may therefore be needed permanently to maintain the structural integrity of the vascular anastomosis. Thirdly, to establish a permanent, nonthrombogenic vessel, the innermost layer should grow together for a continuous, uninterrupted lining of the entire vessel. Thus, it would be preferable to have a stapling instrument that would create vascular anastomosis that are everted, that is folded outward, or that creates direct edge-to-edge cooptation without inversion.
In recent years, methods have been developed in attempt to treat an aortic aneurysm without the attendant risks of intra-abdominal surgical intervention. For example, Komberg discloses in U.S. Pat. No. 4,562,596 “Aortic graft, device and method for performing an intraluminal abdominal aortic aneurysm repair” an aortic graft comprising a flexible tubular material having a plurality of struts along its body, to lend the graft stability and resiliency. The struts have angled hooks with barbs at their upper ends which are securely attached to the inside of the aorta above the aneurysm. Komberg's graft is inserted using a tubular device also disclosed in his patent. Komberg, however, only anchors the proximal end of the graft. Komberg claims that the downward flow of blood holds the distal graft securely in place, so that no mechanical attachment is necessary distally. The blood pressure in the abdominal aorta, however, is typically in the magnitude of 130 mm of mercury (Hg). In spite of the direction of flow of blood through the graft, proximal to distal, substantial back pressure within the aneurysm will result unless the distal end is also mechanically attached to the aorta in a manner that prevents substantial leakage of blood between the graft and the aorta. Without distal attachment, the device of Komberg will not effectively exclude the weakened arterial wall at the site of the aneurysm from the forces and stress associated with the blood pressure.
Another example can be seen in U.S. Pat. No. 4,787,899 “Intraluminal graft device, system and method”, disclosed by Lazarus. Lazarus discloses a grafting system that employs a plurality of staples mounted in the proximal end of the graft. Lazarus's staples are forced through the aorta wall by means of a balloon catheter. Similarly to Komberg, Lazarus uses staples only in the proximal end of the graft. There is no teaching or suggestion as for mechanically attaching the graft to the distal aorta below the level of the aneurysm.
Taheri discloses in U.S. Pat. No. 5,042,707 “Intravascular stapler, and method of operating same” an articulatable stapler for implanting a graft in a blood vessel. The stapler is in the form of an elongated catheter with a plurality of segments mounted on the distal end of the catheter. The segments have beveled faces and are connected to each other by hinges. A wire runs through the catheter to the most distal segment. The most distal segment is moved, in conjunction with the other segments, into a firing position that is substantially perpendicular to the main catheter body by the action of pulling the wire. The staple is implanted by using two other wires that act as fingers to bend the staple into its attachment position.
Taheri, however, appears to be a single-fire design that can only implant one staple at a time. After each stapler is implanted, Taheri's design apparently requires that the catheter will be removed before another staple is loaded. In addition, Taheri does not suggest an appropriate density of staples to secure a graft against the pulsatile blood flow of the aorta. Pressures within the aorta range from 120 mm Hg pressure to 200 mm Hg pressure. Without adequate attachment, the graft may leak around the edges continuing to allow life-threatening pressures to develop in the aneurysm. Moreover, the graft can be even replaced.
Similar inherent defects as the ones referred herein are present in endovascular fastener and grafting apparatus that is disclosed in PCT application published as WO 02/17797. Moreover, it appears that some obstacles for blood flow in the vessel evolve from the wire ends. Other fasteners for the grafts are disclosed in American patent applications US 2003/0176877 by Narciso et al., US 2003/0130671 by Duhaylongsod et al and US 2003/0033005 by Houser et al.
All of the prior references require a sufficiently large section of healthy aorta surrounding the aneurysm to ensure attachment of the graft. The neck of the aorta at the end above the aneurysm is usually sufficient to maintain a graft's attachment means. However, when an aneurysm is located near the iliac arteries, there may be an ill-defined neck or no neck below the aneurysm. Such an ill-defined neck would have an insufficient amount of healthy aortic tissue to which a graft can be connected.
There are a number of shortcomings with the presently available graft products and their fixation within the abdominal aorta. Although sizing of “tube” or “bifurcated” grafts is radiographically assessed prior to surgery, it is necessary for the surgeon to have a large selection of graft lengths and diameters on hand to ensure an appropriate surgical outcome.
Additional shortcomings include the placement of a “circular” profile graft with an associated fixation device within an essentially “ovoid” profile vessel and the use of attachment means which fasten only to the insubstantial, structurally compromised (diseased) intima and media levels of the vessel wall.
Research has exposed yet another problem which indicates that the necks of the post-surgical aorta increase in size for approximately twelve months, regardless of whether the aneurysm experiences dimensional change. This phenomenon can result in perigraft leaks and graft migration
Vascular endoprostheses (stent-grafts) are newly developed surgical procedure designed to reduce the drawbacks of suturing anastomosis procedure. The stents were developed about 10 years ago to avoid major conventional open surgical repair for abdominal aortic aneurysm (AAA). Parodi in 1990 performed the first human stent graft, backed by extensive animal experiments. In this method, incision is made in the patient groin and a catheter is inserted into a blood vessel that leads to the aorta. A stent graft (a Dacron tube inside a metal self expandable metal cylinder) is inserted through the catheter. Once the stent graft is in place, cylinder is expand like a spring to hold tightly against the wall of the blood vessel. Stent graft can be supplied with the ancure device (EVT/Guidant: ANCURE ENDO-HOOKS). The first production endografts to enter clinical trails in the US were approved by the FDA in September 1999 for clinical use under a careful monitored training program.
The treatment of AAA with stent grafts is rapidly evolving field. Several grafts models were introduced (U.S. Pat. Nos. 6,290,731, 6,409,756 are provided herein as references). The stent construction is unique for each type of device. Stents are working in very difficult conditions but there is no knowledge about the long-term durability. Analysis Made by G. Riepe et al. (provided herein as references) shows that the long-term durability of conventional graft is still much higher then ones of stent graft.
Hence, although in recent years certain techniques have been developed that may reduce the stress, morbidity, and risk of mortality associated with surgical intervention to repair aortic aneurysms, none of the systems that have been developed effectively treat the aneurysm and exclude the affected section of aorta from the pressures and stresses associated with circulation. None of the devices disclosed in the references to this patent application provide a reliable and quick means to reinforce an aneurismal artery.